This invention relates to a process for the recovery of sulfuryl fluoride and sulfuryl chlorofluoride substantially free of undesired chlorine contaminant. In accordance with another aspect, this invention relates to a method of preparing sulfuryl chlorofluoride from a reaction mixture of sulfur dioxide, chlorine and hydrogen fluoride.
The preparation of sulfuryl fluoride (SO.sub.2 F.sub.2) from an anhydrous gaseous mixture of sulfur dioxide (SO.sub.2), chlorine (Cl.sub.2) and hydrogen fluoride (HF) in the presence of a catalyst at temperatures of from about 150 to about 450.degree. C., preferably above about 200.degree. C., is conventional in the art. U.S. Pat. Nos. 2,772,144, 3,092,458, and 3,320,030 all relate to such manufacture of SO.sub.2 F.sub.2 while U.S. Pat. No. 2,875,127 relates to the use of SO.sub.2 F.sub.2 as a fumigant. It is the usual prior art practice to pass the SO.sub.2 F.sub.2 product reaction mixture exiting from a reactor through an aqueous scrubber system to recover many of the undesired by-products or unused reactants, e.g., Cl.sub.2, SO.sub.2, HCl and SO.sub.2 ClF, before recovering the final product. The presence of free chlorine in the final product is undesired in view of its highly corrosive nature; such free chlorine cannot readily be distilled from the desired product in view of the azeotrope mixture that Applicants believe forms with sulfuryl fluoride and the use of aqueous scrubbers taught in the art is unsatisfactory as they do not completely remove the free chlorine content. Moreover, these methods suffer other disadvantages on account of numerous attendant pollution problems associated with such aqueous effluent waste streams, as well as the economic loss of valuable unused reactants and hydrogen chloride by-product.
The production of SO.sub.2 ClF by reacting SO.sub.2, HF and Cl.sub.2 in the presence of activated carbon catalyst and an alkali metal bifluoride at 100.degree.-200.degree. C. is also taught by the U.S. Pat. No. 3,320,030 mentioned above. Various other processes utilizing different reactants, e.g., KSO.sub.2 F and Cl.sub.2, SO.sub.2 Cl.sub.2 and SbF.sub.3, CoF.sub.3, AgF.sub.2, MnF.sub.3, NH.sub.4 F, NH.sub.4 HF.sub.2 and the like are also taught in the art but are not considered as pertinent as the teachings of the U.S. Pat. No. 3,320,030.
Accordingly, an object of this invention is to provide an improved process whereby SO.sub.2 F.sub.2 substantially free of chlorine can be obtained without the employment of aqueous scrubbing systems.
Another object of the present invention is to provide a method whereby SO.sub.2 ClF can be produced from excess chlorine contained in an SO.sub.2 F.sub.2 product reaction mixture.
Other objects and aspects, as well as several advantages of the invention, will become apparent upon consideration of the accompanying disclosure and the appended claims.